Method of treating metals.



WITNESSES INVENTOH Mal/m I K? W V f MA F. L. BISHOP. METHOD OF TREAT ING METALS. APPLICATION FILED FEB.26. 19I3.

1,171,832. Patented Feb. 15,1916.

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METHOD OF TREATING METALS.

Specification of Letters Patent.

Patented Feb. 15, 1916.

Application filed February, 1813. Serial Ito. 750,844.

To all whom it may concern: Be it known that I, Fnnnuurc L. -BISI-I0, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Method of Treating Metals, of-

whieh the following is afull, clear, and exact description, reference being had 'to the accompanying drawings, in which the figure is a diagrammatic sectional side elevation showing one form of apparatus for carrying out my .invention.

Heretofore in changing the molecular structure or size of grain of metals, it has been customary to subject them to heat treatment of mechanical work, or both. Thus, it is well known that in annealing, tempering-and hardening processes the heating of the piece, especially beyond certain temperatures, produces a change in structure. Again, simple mechanical work in the way of forging, hammering, rolling, drawing, etc., is'known vto change the structure of the metal.

I have discovered that by subjecting metal to the action of the magnetic field of an alternating current either with or without heating of the metal, the structure or size of-grain of the metal may be altered.

In practice, I prefer to so apply the alternatlng current that the metal will be heated as well 'as subjected to its magnetic field, since the desired change in structure is much more rapidly produced.

Q My invention may be applied to any metal in a solid state and the method of applying the magnetic field of the alternating current may be widely varied without departing from my invention.

In the drawings, in which I show one form of apparatus for carrying out my process, 2 represents an alternating current generator whose leads are connected to the primary regulating transformer 3, the leads from the secondary of this transformer are connected to the terminals of coil 4 of bare copper wire, preferably wound around an asbestos cylinder 5 inclosing the bar of steel to be treated. This may, as in this example, be a round bar of steel, say one and a half inches in diameter. The copper Wire may have say 300 turns and be of No. 4 size and through it I pass an alternating current of say 50 amperes and preferably alternations per second. In thiscase the metal bar is heated by the induced eddy currents therein, as well as acted on by the magnetic of the metal is uniform throughout and the action of the magnetic field in changing the structure is greatly hastened by the heating effect. This treatment is preferably continued; in the example just referred to, until the steel is brought to 'a temperature lower than that employed in the ordinary annealing of steel. Forexample, on a steel Under these conditions, the heating for which 900 C. is recommended for annealing, I have found that the desired result is obtained by my process when a temperature of 750 to 800 C. is reached. The

rate. of rise in temperature is, of course,

off the current.

I preferably surround the article and coil with non-heat conducting material, indicated at 6 in thedrawing, to prevent radiation and conduction of heat and make the method more economical.

If a bar of steel is to be hardened or tempered, it may be treated in the same manner as above described, the bar when it has reached the desired condition, as indicated by its magnetic properties or temperature, or both, being withdrawn and quenchd'or treated in the usual manner for hardening after which it may be returned to the apparatus for further treatment in tempering.

It will be noted that my method is not for mere electrical heating. The desirable effect is obtained not by heating alone, but by the action of the magnetic field of the alternating current onthe molecular structure of the metal being treated.

The advantages of my invention result from the action of the magnetic field of an alternating current upon the metal. This action is found to change the grain or molecular structure of the metal in different ways depending upon how the current is applied. That is, by varying the amount of current, the number of alternations per sec- The bar is then slowly cooled by' 0nd, etc., the structure of the metal may be accurate regulation of the temperature by 

